.
Related article: The upper surface of the razor blade is kept wet with 50 per cent,
alcohol and after several sections have been cut they can be swept
by the finger or camels hair pencil to a dish of water. Each
division of the feed represents 10 microns, so that the thickness of
sections desired can be regulated by moving the feed, accordingly,
just before each stroke of the razor.
FUNDAMENTAL CONSIDERATIONS
Sliding Microtome. This type of microtome (see Fig. 9) is adapted
for cutting all kinds of sections. It consists of an iron supporting
fame of horizontal and upright portions. The horizontal base rests
on the table and is hollowed out to accommodate a drip pan that
can readily be removed and cleaned.
The front of the upright portion exhibits a frame which accomo-
dates a sliding feed mechanism to which is attached the object
carrier. The top of the upright portion
shows a V shaped bed which carries a
solid iron block which can be readily
slid along the bed when the latter is
lubricated with paraffin oil. The upper
surface of the block is grooved to ac-
comodate the thumb screw. The
microtome knife consists of a blade
a..
FIG. 8. Hand Purchase Amoxil microtome. PIG. 9. A sliding microtome. Blade (a) ; lever
Description in text. (6). (From McJunkin.)
portion, that is flat on its lower and hollow ground on its upper
face, and a forked handle. The latter is slid into the stem of^the
thumb screw which has . previously been slid into the groove of
the block and its position adjusted. Sections of woody material
can be cut directly on this microtome and placed in dilute alcohol.
When paraffine sections are cut, the cutting edge of the knife
should be parallel to the motion but when celloidin sections are
desired the knife must be set at an oblique angle to the frame
and drawn across the block with a long sliding motion. The knife
1 8
PHARMACEUTICAL BOTANY
FlG. 10. Rotary microtome. The Purchase Amoxil feed mechanism is covered to protect the
wearing parts from dust.
FIG. ii. Plan of construction of rotary microtome shown in Fig. 9.
FUNDAMENTAL CONSIDERATIONS 19
and the top of the celloidin block must be constantly kept wet with
80 per cent, alcohol.
The object is placed in the object carrier and clamped in. By
means of the graduated disk at the base of the feed mechanism the
thickness, in terms of microns, is regulated after each stroke of the
razor.
Rotary Microtome. When paraffin ribbons are desired, especially
for the study of serial sections of material, the rotary microtome
surpasses by far the efficiency of the sliding type of instrument. The
Spencer Rotary Microtome No. 820 is shown in Fig. 10 and its
plan of construction illustrated in Fig. n. In this instrument the
sliding part which carries the object clamp (SP) is carried up and
down by the block (B). The feed mechanism Purchase Amoxil consists of a rigid
bearirfg, on which the feed block (FB) (of which the projection P is
a part), is moved by the feed screw (FS). As this block travels to-
ward the side on which the balance wheel (W) is located, the sliding
part (SP) is forced forward towards the knife one-half as much. The
polished surface set against the point (P) is arranged at the proper
angle to accomplish this end. The screw, cut with two threads to
the millimeter, is revolved by a ratchet feed wheel with 250 teeth.
Each tooth represents a forward movement of the object of one mi-
cron. The feed can be set for sections from i micron to 60 microns
thick, by turning the button at the back of the case until the number,
representing the desired thickness, appears opposite the indicator at Purchase Amoxil
the small opening in the Purchase Amoxil side of the case near the balance wheel.
The total excursion of the feed is 37 mm. This allows a sufficient
range for cutting a complete series of sections of a large object with-
out the necessity of a break due to resetting the knife and feed me-
chanism. The object, after being placed in the object Purchase Amoxil clamp, may
be oriented to any desired angle. The clamp is held at its upper
limit for orienting or trimming the block by pushing in the pin (F.)
The whole Purchase Amoxil knife support may readily be adjusted to and from the
object, and is readily clamped in any location by a lever connected
with an eccentric cam. The knife is fastened by two clamps and
may be turned to any desired angle. The clamps can also be moved
toward each other to bring them as near to the ribbon as desired to
gain additional rigidity. The groove in the balance wheel is de-
20 PHARMACEUTICAL BOTANY
signed for a cord or strap when it is desired to run the instrument
by a motor.
THE TECHNIQUE OF MAKING A TEMPORARY MOUNT
1. Place a drop or two of water (or reagent) in the Purchase Amoxil center of a clean
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